1. The Field of the Invention
The present invention concerns separation apparatus and methods, and particularly those systems that separate two or more mixed fluid components through centrifugation.
2. Technical Background
Centrifugal systems for separation use centrifugal force generated through rotation to separate fluid components of differing densities. In many fundamental aspects, these systems are used as a substitute for and improvement on gravitational separation techniques and devices, since the gravitational force and the centrifugal force exerted on a fluid through rotation are identical in that they increase in magnitude as the fluid increases in mass. Those fluids with lesser density will be less influenced by the force and therefore less inclined toward the source of the force, the earth for gravitational, the outside of the rotating container for centrifugal, than fluids with greater density. The fluids will thus separate out and can be directed to separate collection ports by using weirs or other suitable separating structures. Centrifugal separation is often more desirable than gravitational because the force applied to the fluid can be controlled through rotation speed and can be made to be many times that of gravity.
A common example of fluid separation is that of oil from water. There are many situations in which separation of these two elements is desired, such as oil spills on an ocean or lake, mixing of the two fluids in a ship's bilge, gasoline spills, etc. The process of fluid separation is often important for maintenance of quality of life in a particular geographic area. These two fluids are susceptible to centrifugal separation because water is more dense than oil and thus will "sink" relative to the other under application of centrifugal force. This can easily be understood by the fact that oil floats on water in a gravitational field. Other fluid separation applications include wine clarification, waste-water treatment, blood plasma separation, and the like. Centrifugation is also used to separate solids out of liquids through sedimentation.
It is often desirable to separate out elements dispersed in solution or emulsion. Standard centrifugal separation equipment alone cannot carry out such a separation since the dissolved elements will move with the solution. A solvent must therefore be introduced into the fluid stream to extract the dissolved elements. Such a process requires that the solvent be thoroughly mixed with the fluid to extract all dissolved elements. The solvent and fluid are then separated through centrifugation. An example of this type of separation is solvent extraction and separation of transuranic elements from radioactive waste streams at nuclear processing plants.
Similarly, it has been found to be beneficial to add emulsion breaking additives to emulsions to cause them to separate under centrifugal action. These emulsion breakers break down the bonds which stabilize the emulsion. The two components which formed the emulsion may then be separated through centrifugation.
While many centrifugal separators have been designed to effect fluid separation on the basis of differential fluid density, such separators generally suffer from a variety of disadvantages. One common shortfall found in prior art centrifugal separators is their limited flow capacity. Many designs have substantial power requirements to overcome the effects of internal fluid shear while achieving rates of rotation necessary to obtain effective separation.
Another disadvantage common in prior art centrifugal separators is the inability to separate fluids having varying density differentials. Many prior art centrifugal separators are designed for a single application, such as separating cream from milk, and work efficiently only when separating fluids that have predetermined densities. Those designs purporting to effectively separate fluids having a broad range of density differentials utilize complicated external control mechanisms to monitor and control the pressures and flow rates within the separator. Besides having only limited effectiveness, such designs are generally complicated to build and operate, making them economically inefficient for use in many applications.
In some situations it is desirable to separate two fluids having substantially similar densities. The separation of emulsions from an unemulsified component is one such situation. For example, when oil is mixed with water, as would occur at a crude oil spill in the sea, wave action often causes the oil to mix with the water to form a stable emulsion. Since many crude oils have densities close to that of water, and the emulsion is primarily composed of water, the emulsion cannot be separated from the water on the basis of density. Typical of prior art solutions to this problem is the application of chemical agents, or "emulsion breakers," that serve to disassemble the emulsion. This process generally results in unsatisfactory results because the processing time required to break up the emulsion requires low volume flow rates through the separator.
From the foregoing, it will be appreciated that it would be an advancement in the art to provide a centrifugal separator for effectively separating fluids having disparate densities which could operate at a substantially higher flow rate than prior art centrifugal separators.
It would be an additional advancement in the art to provide such a separator which would effectively separate fluids having a wide range of density differentials without requiring external control or adjustment of the separator.
It would be a further advancement in the art to provide such a separator having the capacity of separating fluids having similar densities, such as an emulsion, through the use of centrifugal forces.
Such a device and method are disclosed and claimed herein.